AGHS - Chem - Build an Isotope - Matthew Neff | Library

Open the following simulation link in a new tab or view the embed below: https://phet.colorado.edu/sims/html/isotopes-and-atomic-mass/latest/isotopes-and-atomic-mass_en.html

Click the green plus symbols on the righ side to open the symbol and abundance in nature windows.

With hydrogen (atomic number 1) selected, notice the two numbers in the symbol box. Up top is a black "1". On the bottom is a red "1".  Notice the name in the atom says the name, "Hydrogen-1". Drag a gray neutron from the dish into the atom.

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When you added the neutron to the atom, what is the new name? (type it EXACTLY as shown. Do not add any spaces.)

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On the symbol block, which number changed, black or red?

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So if one number stayed the same, and the other one changed, which one is the atomic number and which is the mass number?

Draggable item		Corresponding Item
Red number (bottom)		Atomic number
Black number (top)		Mass number

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So then, which number changes as you add neutrons to the atom?

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What does the number in the isotope name (i.e. the "1" in Hydrogen-1) tell you?

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Does the element change (i.e., does H become He or Li) when you change the number of neutrons?

Change the element to oxygen by clicking on its symbol below the periodic table on the top right.

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In the top left yellow box (showing the numbers of protons, neutrons and electrons in the atom, how many gray neutrons are there?

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Looking at the element block in the yellow "Symbol" box, look at those numbers like they were a subration problem: the top number minus the bottom number. This will also tell you the number of neutrons. Subtract the bottom number (atomic number) from the top (mass number). What do you get?

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As you keep adding neutrons, the atom (and nucleus) will eventually become unstable. What is the lowest total number of neutrons that results in an unstable isotope of oxygen?

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What is the name of this unstable isotope from number 9?

Continue playing around with the sumulation to see if what you learned above remains true for each element.